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Technical Paper

Use of Alternative Transportation Fuels and Its Environmental Implications in Canada

1991-09-01
911695
Motor vehicles using gasoline and diesel fuel are major contributors to atmospheric pollution. There are several alternative fuels that are potentially cleaner than current gasoline and diesel fuel. Exhaust emission measurements of regulated and non-regulated pollutants using a number of alternative fuels including low level alcohol-gasoline blends, natural gas, propane, and methanol in selected vehicles show certain environmental/air quality benefits and indicate future potential to further reduce the motor vehicle emissions.
Technical Paper

Evaluation and Study on the Heat Release Rate of Swirl Chamber Diesel Engine

1991-09-01
911786
A zero-dimensional computation model for the heat release rate of a swirl chamber diesel engine is established in this paper. With the aid of control volume analysis method of variable mass thermodynamic system, the instantaneous discharge coefficent of the connecting passage of combustion chambers is accurately determined by calculating the motored indicator diagrams of main and swirl chambers. A deeper study is also made on the heat release rate and other combustion characteristics under various conditions of the swirl chamber diesel engine such as connecting passages with different structural parameters, different shapes of main combustion chambers and different operating conditions. Thus some beneficial conclusions are reached, that is, the combustion delay in the main combustion chamber of the swirl chamber diesel engine is an important reason for its fuel economy lower than that of a DI diesel engine besides its greater losses of flow and heat.
Technical Paper

VR/LE Engine Concept Application to the Turbocharged Diesel Engine

1991-09-01
911788
A variable compression ratio concept that can give a different expansion ratio to the compression ratio has been evaluated by means of a simulation of a turbocharged diesel engine. The VR/LE mechanism kinematics have been defined and described, and the compression ratio and expansion ratio have been presented as a function of the eccentric phase angle (αo). A zero-dimensional engine simulation that has been the subject of comprehensive validation, has been used as the basis of the VR/LE study. The effect of the compression ratio on the engine performance at fixed loads is presented. The principal benefits are a reduction in fuel consumption at part load of about 2%, and a reduction in ignition delay that leads to an estimated 6 dB reduction in combustion noise. The study has been conducted within the assumption of a maximum cylinder pressure of 160 bar.
Technical Paper

Chemistry Implications from Optical Diagnostics in Engine Research

1991-09-01
911784
Modern optical diagnostics such as laser induced fluorescence (LIF) offer considerable assistance in developing effective computational capabilities for complex reactive flows. Applications of these selective, spatially-resolved, non-intrusive technologies include model verification, input parameters, and kinetic simplifications for complex calculations. Pertinent examples from our current diagnostics development and flame applications are reviewed with an emphasis on the chemical implications to advanced computational dynamics for engines. Raman, LIF, and chemiluminescence diagnostics are discussed; potential diagnostics applications include fluid mixing, pollutants, knock, flame front location, and temperature measurement.
Technical Paper

The Effects of Spray, Mixing, and Combustion Model Parameters on KIVA-II Predictions

1991-09-01
911785
The combustion process in a diesel engine was simulated using KIVA-II, a multi-dimensional computer code. The original combustion model in KIVA-II is based on chemical kinetics, and thus fails to capture the effects of turbulence on combustion. A mixing-controlled, eddy break-up combustion model was implemented into the code. Realistic diesel fuel data were also compiled. Subsequently, the sensitivity of the code to a number of parameters related to fuel injection, mixing, and combustion was studied. Spray injection parameters were found to have a strong influence on the model's predictions. Higher injection velocity and shorter injection duration result in a higher combustion rate and peak pressure and temperature. The droplet size specified at injection significantly affects the rate of spray penetration and evaporation, and thus the combustion rate. Contrary to expectation, the level of turbulence at the beginning of the calculation did not affect fuel burning rate.
Technical Paper

Electromagnetic Compatibility in the Off-Highway Vehicle

1991-09-01
911791
Abstract The key words in the marketplace for off-highway vehicles are durability, performance, and efficiency. A manufacturer of these vehicles recognizes that one way to successfully address these needs is by a well thought through electronics design. With the computer sophistication now being incorporated into off-highway vehicles, engineers must work closely to assure electromagnetic compatibility (EMC) of the entire system. A properly established EMC program extending from concept to final design will support each of a product's specified operations and still function as an integrated whole. This paper describes the process for designing the EMC for an off-highway vehicle.
Technical Paper

Hydraulic Control System for a Corn Detasseler

1991-09-01
911792
Performance specifications for a corn detasseler position control system were determined. An electrohydraulic position control system was designed and bench tested against the specifications. The bench prototype utilized three different actuators, a 2 inch diameter cylinder, a 6.4 in3 motor, and a 3.0 in3 motor. Each prototype system was tested with a basic carrier bracket load and a complete detassaling assembly load. With a supply of 10 gpm at 2000 psi, a 6.4 in3 motor met the performance requirements. With the same supply, the 2 inch diameter cylinder system was too slow and the 3.0 in3 motor system was unstable.
Technical Paper

3-D Modeling of Diesel Engine Intake Flow, Combustion and Emissions

1991-09-01
911789
Manufacturers of heavy-duty diesel engines are facing increasingly stringent, emission standards. These standards have motivated new research efforts towards improving the performance of diesel engines. The objective of the present program is to develop a comprehensive analytical model of the diesel combustion process that can be used to explore the influence of design changes. This will enable industry to predict the effect of these changes on engine performance and emissions. A major benefit of the successful implementation of such models is that engine development time and costs would be reduced through their use. The computer model is based on the three-dimensional KIVA-II code, with state-of-the-art submodels for spray atomization, drop breakup / coalescence, multi-component fuel vaporization, spray/wall interaction, ignition and combustion, wall heat transfer, unburned HC and NOx formation, and soot and radiation.
Technical Paper

Energy Requirements for the Space Frontier

1991-09-01
912064
Abstract The future appears rich in missions that will extend the frontiers of knowledge, human presence in space, and opportunities for profitable commerce. Key to success of these ventures is the availability of plentiful, cost effective electric power and assured, low cost access to space. While forecasts of space power needs are problematic, an assessment of future needs based on terrestrial experience has been made. These needs fall into three broad categories survival, self sufficiency and industrialization. The cost of delivering payloads to orbital locations from LEO to Mars has been determined and future launch cost reductions projected. From these factors, then, projections of the performance necessary for future solar and nuclear space power options has been made. These goals are largely dependent upon orbital location and energy storage needs. Finally the cost of present space power systems has been determined and projections made for future systems.
Technical Paper

Small Stirling Dynamic Isotope Power System for Multihundred-Watt Robotic Missions

1991-09-01
912066
Free-piston Stirling engine (FPSE) and linear alternator (LA) technology is combined with radioisotope heat sources to produce a compact dynamic isotope power system (DIPS) suitable for multihundred-watt space applications which appears competitive with advanced radioisotope thermoelectric generators (RTGs). Unlike earlier DIPS concepts based on closed cycle Brayton conversion, the small Stirling DIPS is scaleable to multihundred-watt power levels or lower. The FPSE/LA convertor, which is not subject to the tip clearance to swept area scaling limitation of turbomachinery, remains a high efficiency convertor in sizes ranging from tens of kilowatts down to only a few watts.
Technical Paper

In-Flight Simulation of Backside Operating Models Using Direct Lift Controller

1991-09-01
912069
Effectiveness of a direct lift controller (DLC) for in-flight simulation is discussed. When a model aircraft is operating in backside of power curve, DLC is indispensable. On the basis of this, a quick-moving flaps are installed on the variable stability and response airplane (VSRA) of the National Aerospace Laboratory of Japan. Direct lift capability of the flaps are precisely identified. After tailoring adequate feedback/feed forward gains, a model-following system is constructed to simulate backside-operating models by a mother airplane which is operating in frontside. Included in the paper are the test results of flight verification, showing that a direct lift controller is helpful but not mandatory for simulating frontside-operating models, while it is mandatory for simulating backside-operating models with model-following error of acceptable level. As an application, a flight test result for simulated landing approach in backside range is shown.
Technical Paper

Electrical System Options for Space Exploration

1991-09-01
912065
The Space Exploration Initiative (SEI) will need a wide variety of manned systems with requirements significantly different than those for existing systems. This paper discusses the need for a space power utility concept, and examines the impact of this concept on the engineering of space power systems. Almost all existing space power systems distribute low voltage direct current. Although they have been very successful, increasing power system requirements in recent years have exposed their inherent limitations and led to the proposal of a number of alternatives including high voltage dc, and ac at various frequencies. This paper, drawing on the experience gained from Space Station Freedom and SEI systems studies, discusses the factors that may affect the choice of frequency standards on which to build such a space power utility.
Technical Paper

A Simulator Study of a Flight Reference Display for Powered-Lift STOL Aircraft

1991-09-01
912067
Abstract The present study deals with a proposed flight reference display for powered-lift STOL aircraft. The display design was aimed at providing pilots with new control cues for keeping its flight safety in low-speed and high-power approach. The display utilizes angle of attack, pitch angle and airspeed to indicate the flight reference for maintaining the flight safety margins. The display integrates the flight reference into an analogue airspeed scale. Piloted simulation using a moving-base flight simulator was conducted to verify the display which was designed on the basis of the flight test results of “ASKA”, the experimental STOL aircraft of National Aerospace Laboratory. The test results confirmed that performance of the display was satisfactory for both flight reference tracking and safety margin monitoring, and proper values of coefficients of the display equations were obtained.
Technical Paper

Socio-Cultural Issues During Long Duration Space Missions

1991-09-01
912075
Future space missions will involve multi-national crews of men and women who will perform complicated tasks over long periods of time. Under these conditions, social and cultural factors will play a significant role in influencing crew morale, cohesiveness, and performance. Important socio-cultural issues include language differences between crew members, cultural and racial biases, gender stereotyping, and differences in career motivation. Negative aspects of these issues include the scapegoating and isolation of individuals who are seen as different from the rest of the crew; the formation of subgroups, which creates divisiveness and unhealthy competition; the presence of interpersonal tension, which leads to decreased cohesiveness and increased withdrawal and territorial behavior; and the displacement of tension and anger to colleagues and families on Earth, which leads to poor crew-ground communications.
Technical Paper

Aerospace Plane Hydrogen Scramjet Boosting

1991-09-01
912071
Abstract The results of computational investigations carried out to clarify the possibilities of hydrogen scramjet thrust uprating in hypersonic flight (M >8) by adding to the fuel substances with higher density are presented. Thrust, specific impulse and density impulse are calculated while adding nitrogen, oxygen, water or inert liquated gases. Fuel is injected tangentially to air flow into combustion chamber with high velocity through gas generator nozzles. For scramjet boosting in hypersonic flight it is suggested to add oxygen to stoichiometric part of hydrogen instead of excessive part of hydrogen.
Technical Paper

Runway Incursions and Airport Surface Traffic Automation

1991-09-01
912123
Runway incursions occur when aircraft or vehicles get onto a runway and conflict with aircraft cleared to land or take off on that same runway. All are caused by human error. The Federal Aviation Administration has identified reducing these human errors as a safety priority. Application of new technology is part of the solution. This paper highlights recent actions by the agency in addressing runway incursions and discusses a strategy for development of airport surface traffic automation designed to aid the air traffic controller and the pilot in identifying potential runway incursions. Airport surface traffic automation represents a conflict alert system which adds both automated safety monitoring and tools for the controller to use in reducing surface movement delays.
Technical Paper

Comparison of Elastic and Rigid Blade-Element Rotor Models Using Parallel Processing Technology for Piloted Simulations

1991-09-01
912120
A piloted comparison of rigid and aeroelastic blade-element rotor models was conducted on the Crew Station Research and Development Facility (CSRDF) at Ames Research Center. FLIGHTLAB, a new simulation development and analysis tool, was used to implement these models in real time using parallel processing technology. Pilot comments and quantitative analysis performed both on-line and off-line confirmed that elastic degrees of freedom significantly affect perceived handling qualities. Trim comparisons show improved correlation with flight test data when elastic modes are modeled. The results demonstrate the efficiency with which the mathematical modeling sophistication of existing simulation facilities can be upgraded using parallel processing, and the importance of these upgrades to simulation fidelity.
Technical Paper

A Review of Recent Programs and Future Plans for Rotorcraft In-Flight Simulation at Ames Research Center

1991-09-01
912121
A new flight research vehicle, the Rotorcraft-Aircrew Systems Concepts Airborne Laboratory (RASCAL), is being developed by the U.S. Army and NASA at Ames Research Center. The requirements for this new facility stem from a perception of rotorcraft system technology requirements for the next decade together with operational experience with the Boeing Vertol CH-47B research helicopter that was operated as an in-flight simulator at Ames during the past 10 years. Accordingly, both the principal design features of the CH-47B variable-stability system and the flight-control and cockpit-display programs that were conducted using this aircraft at Ames are reviewed. Another U.S. Army helicopter, a Sikorsky UH-60A Black Hawk, has been selected as the baseline vehicle for the RASCAL. The research programs that influence the design of the RASCAL are summarized, and the resultant requirements for the RASCAL research system are described.
Technical Paper

Electro-Modulated Control of Supply Pressure in Hydraulic Systems

1991-09-01
912119
Hydraulic power requirements of military aircraft have increased significantly over the years. This has brought to the surface such issues as how best to manage the higher power requirements, which in many cases exist for only a small part of the duty cycle duration, and also how to minimize the system losses (heat rejection), which in turn can result in reduced cooling requirements. This paper summarizes some of the available data on the power requirements of military aircraft, discusses the inefficiencies of higher pressure systems being considered for high horsepower requirements, and describes the available approaches for better management of the high pressure/horsepower requirements, with respect to improving the operating efficiency of such systems.
Technical Paper

Application of Laminar Flow Control to the High Speed Civil Transport - the NASA Supersonic Laminar Flow Control Program

1991-09-01
912115
A balanced program involving both the National Aeronautics and Space Administration (NASA) and industry has been structured to carry out a Supersonic Laminar Flow Control (SLFC) program. The program utilizes a balanced mix of computational efforts, ground facility experiments, and flight testing. Advanced Computational Fluid Dynamic (CFD) methods and boundary-layer stability codes offer the opportunity to analyze flow phenomena to a greater level of accuracy than in the past, yet the computational prediction and design tools need considerable development and validation for the highly three-dimensional supersonic flow conditions of the F-16XL and the High Speed Civil Transport (HSCT). Swept-wing model experiments are underway in a low-disturbance supersonic tunnel to provide data on leading-edge transition physics and flow mechanisms. On-going F-16XL-1 flight tests are obtaining laminar-flow data that will reduce the risk for the NASA experiment on the F-16XL-2.
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